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Line-strength indices in bright spheroidal galaxies: Evidence for a stellar population dichotomy between spheroidal and elliptical galaxies

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Gorgas García, Francisco Javier and Pedraz, Santos and Guzmán, Rafael and Cardiel López, Nicolás and González, J. J. (1997) Line-strength indices in bright spheroidal galaxies: Evidence for a stellar population dichotomy between spheroidal and elliptical galaxies. Astrophysical journal, 481 (1). L19-L22. ISSN 0004-637X

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Official URL: http://dx.doi.org/10.1086/310647


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Abstract

We present new measurements of central line-strength indices (namely, Mg-2, (Fe), and H beta) and gradients for a sample of six bright spheroidal (Sph) galaxies in the Virgo Cluster. Comparison with similar measurements for elliptical (E) galaxies, galactic globular clusters (GGCs), and stellar population models yield the following results: (1) in contrast with bright E galaxies, bright Sph galaxies are consistent with solar abundance [Mg/Fe] ratios; (2) bright Sph galaxies exhibit metallicities ranging from values typical for metal-rich GGCs to those for E galaxies; (3) although absolute mean ages are quite model dependent, we find evidence that the stellar populations of some (if not all) Sph galaxies look significantly younger than GCCs; and (4) Mg-2 gradients of bright Sph galaxies are significantly shallower than those of E galaxies. We conclude that the dichotomy found in the structural properties of Sph and E galaxies is also observed in their stellar populations. A tentative interpretation in terms of differences in star formation histories is suggested.


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© 1997. The American Astronomical Society. All rights reserved. We are grateful to the anonymous referee, A. Aragón Salamanca, J. Gallego, and R. Peletier for useful comments. The INT is operated on the island of La Palma by the RGO at the Observatorio del Roque de los Muchachos of the Instituto de Astrofísica de Canarias. This work was supported in part by the Spanish grant PB93-456. R. G. acknowledges funding from the Spanish MEC fellowship EX93-27295297 and NSF grant AST91-20005.

Uncontrolled Keywords:Galactic globular-clusters; Dwarf galaxies; Virgo cluster; Gradients
Subjects:Sciences > Physics > Astrophysics
Sciences > Physics > Astronomy
ID Code:29955
Deposited On:21 May 2015 08:21
Last Modified:10 Dec 2018 15:05

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